Various types of vaporizing apparatus have been known for treating air. Watkins, U.S. Pat. No. 3,923,934, issued Dec. 2, 1975, shows a device for vaporizing a liquid into the air to control odors. Such a device is more broadly applicable to the dispensing of liquids, including odorants, deodorants, and air fresheners.
The Watkins device includes a chamber in which a liquid is vaporized by passing air through a coiled, corrugated element. The liquid is sealed within ridges in the corrugated element, which is described in further detail in Watkins, U.S. Pat. No. 3,885,737, issued May 27, 1975.
In the Wilkins '934 patent, an inlet port in a front wall of the chamber communicates with a central tube formed by the element along its longitudinal axis when the element is coiled. An outlet port is also provided in the front wall of the chamber, radially outward from the inlet port. A disc-shaped shutter is rotated to simultaneously control the opening of the inlet and outlet ports on the front side of the air flow chamber.
Air is circulated first through the inlet port and the central tube in the coiled element. It then passes radially outward, and is then drawn back through the coiled element and out of the outlet port to be mixed with air from the outside. The vapor is then blown outside the unit by a motorized fan.
In this prior device, the air flows through a somewhat complex path, and the control mechanism has many parts. It would be beneficial to provide a more efficient air flow control mechanism, that could be manufactured at lower cost.
Replacement of the vaporizing element in the Watkins unit was not as convenient as desired. This was improved in a later version by providing a replaceable cartridge in a cylindrical canister. To replace the cartridge, a housing end plate was removed and the cartridge was inserted into a housing chamber. In this version, positioning of the inlet and outlet ports in the front end or top of the cartridge could not be easily observed, because the front end was inserted first into the housing chamber.